1. Field of the Invention
The present invention relates generally to inkjet printing and specifically to the use of dielectric heating within an inkjet nozzle to expel a drop of ink.
2. Related Art
Inkjet printers work by squirting ink onto paper. They are non-impact printers in the sense that there is no physical contact between the paper and the print head to render images on a sheet of paper (or other medium). Unlike other non-impact printers, such as laser printers, inkjet printers use aqueous ink to create the images on the paper.
A typical inkjet print head comprises a plurality of nozzles which can simultaneously impart ink from the nozzle to the paper. Presently, the two major types of nozzles in widespread use are thermal nozzles and piezoelectric nozzles.
The performance of the thermal nozzle is constrained by the ability of the nozzle to dissipate heat from a heating element contained in the nozzle to heat the ink. Because the heating element is electrically and thermally coupled to the substrate controlling the nozzle, heat must be dissipated from the substrate. Overheating can lead to damage to the print head and controlling circuitry. The issue of heat dissipation limits the speed of printing, the density of nozzles and the number of nozzles that can simultaneously fire. Because not all nozzles can fire simultaneously, multiple passes must be made when high density color is required such as in photo quality printing.
Piezoelectric nozzles require complex waveforms to “wiggle” drops out of the nozzle requiring greater complexity and size to the print head control circuits. Furthermore, most piezoelectric crystals included in piezoelectric nozzles operate at higher voltages than standard control circuitry.